Manufacturing disk drives is a very competitive business. People that buy disk drives are demanding more and more for their money. For example, they want disk drives that are more reliable and have more capabilities. One way to provide more capabilities is to make the various disk drive parts smaller and to have the slider glide closer to the disk's surface.
Typically a hard disk drive (HDD) uses an actuator assembly for positioning read/write heads at the desired location of a disk's surface to read data from and/or write data to the disk's surface. The read/write heads can be mounted on what is known as a slider. Generally, a slider provides mechanical support for a read/write head and electrical connections between the head and the drive.
The rotation of a disk around the spindle causes air to move beneath a slider. The slider can glide over the moving air at a uniform distance above the surface of the rotating disk, thus, avoiding contact between the read/write head and the surface of the disk. It is important that the air bearing surface (ABS) of the slider is smooth so that it glides properly.